i apologize Geo, i meant to respond to this days ago, and got caught up in my own little world. i think putting 4 in that tank would be pushing it, unless (i always have an unless) you have a confirmed 2 males and 2 females. mantellas are weird, females stay on the floor, while the males pick out a territory and climb high to defend it. so you would have 2 occupying the ground and 2 occupying the land. that would most likely work.
humidity, i keep mine in the high 70's. i don't heat my tank, and the tank is in a relatively unheated basement. i have a space heater to keep my part of the man/frog/fish cave at a nice 70. so they get cooler temps at night and warmer temps during the day. not as extreme as what is outside, but more like their natural habitat. and remember, if you plan on breeding them, this would be their cold, dry season (June for them). i have links for the climate of Madagascar if you need them. yeah, i researched thoroughly before i built....LOL
oh, and they are wonderful little interior decorators. one of my males has dug out a spot to hide under my oak leaf fig and the females are constantly rearranging little things on the floor. subtle changes, but i notice them. i need to stop staring at my tanks for so long...lol
btw, i just ordered 8 of those little cuties tonight, i should have them this week![]()